The mechanisms controlling neural crest migration during craniofacial development are not well understood. The Eph/Ephrin cell signaling receptor-ligand pair has been identified as playing crucial roles during development, including controlling neural crest cell (NCC) migration. The ephrin-B ligands are also capable of transducing reverse signaling by virtue of their cytoplasmic C-terminal PDZ binding domain. In the case of ephrin-B1, this reverse signaling via the PDZ-binding domain is crucial for the proper migration of neural crest cells and normal craniofacial development. There are two specific aims for this application. First, I propose to identify and characterize mediators of ephrin-B1 reverse signaling during craniofacial development using an immunoprecipitation approach in NCCs. Second, I propose to identify and functionally characterize transcriptional targets of ephrin-B1 reverse signaling by inducing reverse signaling using a soluble EphB2-Fc fusion receptor in primary NCC culture and comparing expression profiles. The goal of this application is to understand molecular mechanisms of ephrin-B1 reverse signaling during craniofacial development. [unreadable] [unreadable] [unreadable]